1. Field of the Invention
The present invention relates to an image sensing apparatus such as a digital camera, and more specifically to an image sensing apparatus having a function to remove effects due to a foreign substance such as foreign particles or dust in an image sensing light path, and to a control method and program thereof for that image sensing apparatus.
2. Description of the Related Art
In an image sensing apparatus such as a digital camera, a foreign substance (hereinafter, abbreviated as ‘dust’) such as foreign particles or dust may become affixed to the surface of an optical member such as an optical filter disposed in an image sensing light path in front of an image sensor. In this case, an effect caused by the affixed dust is reflected in sensed images, decreasing the image quality. Particularly in a digital camera with a removable lens, mechanically operating portions such as a shutter and a quick return mirror are disposed near the image sensor, and dust from those operating portions may be affixed to the image sensor or the optical filter. Also, when exchanging lenses, dust may enter the camera body from the lens mount opening, causing deterioration in photographed images.
In order to address such problems, a removable-lens digital camera provided with an operating mode for removing dust affixed inside the camera has been proposed. This operating mode is, for example, referred to as a cleaning mode. When the cleaning mode is set in the camera, the camera shutter opens and the quick return mirror is raised up, and this state is maintained. In this state a user can view the image sensor or the optical filter from the lens removal/attachment opening via the shutter opening. Thus the user can perform cleaning work such as blowing off dust affixed to the image sensor or the optical filter with a blower (JP 2001-159777A (Document 1)).
Also, in JP 2002-204379A (Document 2), a technique is proposed in which by vibrating a protective glass that protects the image sensor, dust affixed to that glass is knocked off. Further, in JP 2004-172820 (Document 3), a digital camera is proposed that has a means to detect the position of dust in a sensed image, reflects the position of the detected dust in the sensed image, and corrects that portion of the image.
However, in above Documents 1 and 2, although a removal means to knock off dust affixed on the optical member is disclosed, there is no disclosure with respect to processing of dust that could not be completely knocked off. Thus, it is not possible to completely exclude the possibility that dust that could not be completely knocked off will be reflected in a sensed image. Document 3 discloses detecting a position of dust on the image sensor, and correcting the portion of a sensed image. However, there is no disclosure with respect to a means to knock dust off of the image sensor. Thus, in a case that dust increases due to continued taking of photographs, there is a risk of performing excessive image correction processing, thus diminishing the quality of sensed images.
Also, upon detecting the position of dust on the sensor element and obtaining correction data for correcting portions of a sensed image to correct photographed image data, if the dust has been removed by a dust removal unit, it becomes a problem to coordinate the dust removal operation performed by the dust removal unit with the correction data of the sensed image.